Both UV and visible light absorbers are known as ingredients for polymeric materials used to make ophthalmic lenses, and such absorbers may be used in combination with each other. These absorbers are preferably covalently bound to the polymeric network of the lens material instead of simply physically entrapped in the material to prevent them from migrating, phase separating or leaching out of the lens material. Such stability is particularly important for implantable ophthalmic lenses where the leaching of the absorber may present both toxicological issues and lead to the loss of visible light blocking activity in the implant.
Many absorbers contain conventional olefinic polymerizable groups, such as methacrylate, acrylate, methacrylamide, acrylamide or styrene groups. Copolymerization with other ingredients in the lens materials, typically with a radical initiator, incorporates the absorbers into the resulting polymer chain. Incorporation of additional functional groups on an absorber may influence one or more of the absorber's light-absorbing properties, solubility or reactivity. If the absorber does not have sufficient solubility in the remainder of the ophthalmic lens material ingredients or polymeric lens material, the absorber may coalesce into domains that could interact with light and result in decreased optical clarity of the lens.
Examples of visible light absorbers suitable for use in intraocular lenses can be found in U.S. Pat. No. 5,470,932. What is needed are additional visible light absorbing compounds that are copolymerizable with other ingredients in implantable lens materials, relatively inexpensive to synthesize, and are efficient in absorbing light between approximately 380-495 nm.